AI and programming classes in Stevenage

The learner downloads the 101 single-year counts for Stevenage into a Python list called ages, where ages[0] is babies under one and ages[100] is everyone aged 100 or more. The slow way to answer "how many are 11 to 15?" is to loop from index 11 to 15 and add. The prefix sum way builds a second list, P, once: P[0] is 0, and each P[i+1] is P[i] plus ages[i]. After that, the count for ages a to b is P[b+1] minus P[a], two lookups however wide the range.

The trap is the edge. Writing P[b] minus P[a] looks natural and runs without any error, but it quietly leaves out the top age. For "16 and 17" it returns 990, dropping all 1,053 seventeen-year-olds; for "5 to 10" it returns 5,924 instead of 7,125. The learner writes tests that the program must pass: a range of one age must equal that single count, the full range must equal the published 89,501, and two ranges that meet must add up to the combined range.

Once the list is built, questions become instant. Stevenage has 71,562 residents aged 6 to 67, 80.0 per cent of the borough, against 78.0 per cent across England. The learner can then load England's 101 numbers into the same function and compare any range side by side, and notice that the two percentages come from the same code, just different data.

Testing the edges of code an AI writes is a strong reason for Stevenage teenagers to keep learning programming in 2026. The longer argument is in why teenagers should still learn to code in 2026.